The present invention relates to electrical machines, and more particularly, to systems and methods for controlling the torque output by an electrical machine.
An electrical machine, such as an induction motor, is capable of producing torque in response to a drive command. For example, in an electric vehicle or a hybrid electric vehicle, the drive command may be a function of the accelerator pedal position. So, as the operator of the vehicle depresses the accelerator pedal, a drive command is sent to the motor resulting in a given amount of torque being transferred through the vehicle""s transmission and to the tires, where the given amount of torque depends on the accelerator pedal position. The amount of torque or change-in the torque produced by the motor affects the xe2x80x9cdrivabilityxe2x80x9d of the vehicle, where the drivability is the feel and handling of the vehicle from the perspective of the operator or driver.
Further, other factors affect the drivability of the vehicle associated with the torque produced by the motor. For example, the speed and direction of travel of the vehicle, and hence the rotations per minute (rpm) and the direction of rotation of the motor, affect the torque and/or change in torque felt by the operator of the vehicle. For instance, the operator is more likely to sense a change in torque at low speeds, as opposed to high speeds, due to the inertia of the vehicle and the inertia of the motor.
Additionally, the transmission or gear ratio may affect the drivability of the vehicle associated with the torque produced by the motor. The transmission or gear ratio is the ratio of the rpm output by the motor to the rpm of tires or driving axle. For example, the drivability of a vehicle with a relatively high gear ratio is more affected by a change in motor torque than a vehicle with a lower gear ratio.
Thus, systems and methods are desired to control the amount of torque output by an electrical machine to enhance, for example, the drivability of an associated vehicle.
The present invention controls an output torque of an electrical machine by processing input commands and feedback signals to smoothly transition the value of the output torque to achieve the value of a desired output torque as represented by the input commands.
In one embodiment, an electrical machine, comprises: a motor operable to produce a predetermined output torque based on a drive command; a torque controller operable for receiving a motor input command and generating the drive command, the torque controller comprising an input modulator having: a hysteresis module having a predetermined hysteresis function, wherein the hysteresis module is operable for receiving the motor input command and generating a hysteresis signal according to the hysteresis function; a shaping module having a predetermined shaping function, wherein the shaping module is operable for receiving the hysteresis signal and generating a shaping signal according to the shaping function; a filtering module having a predetermined filtering function, wherein the filtering module is operable for receiving the shaping signal and generating a filtering signal according to the filtering function; and wherein the filtering signal comprises the drive command.
In another embodiment, an electrical machine, comprises: a motor operable to produce a predetermined output torque in a predetermined torque direction based on a drive command; a sensor system operable to estimate or detect an actual output torque and an actual torque direction and generate a feedback signal representative thereof; a torque controller operable for receiving a motor input command and the feedback signal and generating the drive command, wherein the motor input command represents a desired output torque and a desired torque direction, the torque controller comprising a speed modulator having: a torque analyzer operable for selecting one of a plurality of slew rates, based on the motor input command and the feedback signal, and operable for generating the drive command as a function of the selected slew rate, the motor input command and the feedback signal.
In another embodiment, an electrical machine comprises: a motor operable to produce a predetermined output torque based on a drive command; a sensor system operable to estimate or detect an actual output torque and an actual torque direction and generate a feedback signal representative thereof; a torque controller operable for receiving a motor input command and the feedback signal and generating the drive command, wherein the motor input command represents a desired output torque and a desired torque direction, the torque controller comprising an input modulator and a speed modulator; the input modulator comprises: a hysteresis module having a predetermined hysteresis function, wherein the hysteresis module is operable for receiving the motor input command and generating a hysteresis signal according to the hysteresis function; a shaping module having a predetermined shaping function, wherein the shaping module is operable for receiving the hysteresis signal and generating a shaping signal according to the shaping function; and a filtering module having a predetermined filtering function, wherein the filtering module is operable for receiving the shaping signal and generating a filtering signal according to the filtering function; the speed modulator comprises: a torque analyzer operable for selecting one of a plurality of slew rates, based on the filtering signal and the feedback signal, and operable for generating the drive command as a function of the selected slew rate, the filtering signal and the feedback signal.
In yet another embodiment, a method of controlling an amount of torque produced by an electrical machine, comprises: receiving a raw accelerator position signal (APS) representative of an actual accelerator position; receiving relative accelerator position signal representative of a change in the actual accelerator position; generating a first adjusted APS according to a predetermined hysteresis function and based on the raw APS and the relative accelerator position; generating a second adjusted APS according to a predetermined shaping function and based on the first adjusted APS, where the second adjusted APS lags or leads the raw APS; generating a third adjusted APS according to a predetermined filtering function based on the second adjusted APS, where the filtering function includes a predetermined modulation factor that varies depending upon the relative accelerator position; and controlling the amount of torque produced by the electrical machine based on a torque command, where the torque command comprises the third adjusted APS.
In yet another embodiment, a method of controlling an amount of torque produced by an electrical machine, comprises: receiving an input torque command representative of an actual accelerator position and a relative accelerator position; receiving a feedback signal representative of an actual rotational direction of a motor associated with the electrical machine; selecting one of a plurality of slew rates based on the input torque command and the feedback signal; and generating a drive command to control the amount of torque produced by the electrical machine, where the drive command is a function of the selected slew rate and the input torque command.
In another embodiment, a method of controlling an amount of torque produced by an electrical machine, comprises: receiving a raw accelerator position signal (APS) representative of an actual accelerator position; receiving relative accelerator position signal representative of a change in the actual accelerator position; generating a first adjusted APS according to a predetermined hysteresis function and based on the raw APS and the relative accelerator position; generating a second adjusted APS according to a predetermined shaping function and based on the first adjusted APS, where the second adjusted APS lags or leads the raw APS; generating a third adjusted APS according to a predetermined filtering function based on the second adjusted APS, where the filtering function includes a predetermined modulation factor that varies depending upon the relative accelerator position; receiving a feedback signal representative of an actual rotational direction of a motor associated with the electrical machine; selecting one of a plurality of slew rates based on the third adjusted APS and the feedback signal; and generating a drive command to control the amount of output torque produced by the electrical machine, where the drive command is a function of the selected slew rate and the third adjusted APS.